1. Field of the Invention
The present invention relates to a surface-emitting type light-emitting diode, and more particularly, to a surface-emitting type light-emitting diode that can accurately measure a distance by emitting light only from a desired surface thereof. The present invention is further directed to a method for fabricating such a surface-emitting type light-emitting diode.
2. Description of the Related Art
Generally, a light-emitting diode (LED) is a device converting an electric energy into a light energy with a high efficiency to thereby obtain a high output at a low current. In addition, the LED has a high response speed, and enables the high-frequency modulation. Furthermore, the LED is designed such that the light output thereof can be readily varied by a current control and it is controlled by either a direct or alternating current.
Such an LED can be employed to a variety of applications such as a sensor device and a distance-measuring device as it can be designed to be small-sized and lightweight with a long lasting and low power consumption. Particularly, the LED has been used as a device for measuring a distance in an iris scan system.
As is well known, the iris scan system is a security system to certify a personal identification to allow only the certified person to enter into a limited area or to access limited information. The iris scan system has a high recognition rate and accuracy compared with a fingerprint scan system.
The iris scan system takes a photograph of an iris, makes image data by image-processing a typical pattern of the photographed image, and compares the image data with a pre-registered iris data, thereby certifying a personal identification.
In such an iris scan system, a position sensitive detector (PSD) for measuring a distance to a user has been used. The PSD has a light emission part and a light reception part. When light is emitted from the light emission part, the light reception part receives the light reflected from an object to measure the distance between the object and the PSD using a triangular surveying. However, the PSD is too expensive to be employed to the iris scan system that should be widely used with moderate prices. In addition, the PSD occurs frequent errors in measuring the distance.
Accordingly, a low-priced iris scan system using the LED has been developed to measure the distance by catching a location of the LED appearing on a photographed image. That is, by installing a pre-calculated algorithm in the iris scan system, the distance to the object can be accurately and quickly measured by detecting the location of the LED appearing on the photographed image.
However, such a conventional surface-emitting type LED has a problem that can be described in conjunction with FIG. 1 showing a side-emitting problem of the conventional surface-emitting type LED.
That is, as shown in FIG. 1, even with a masking process, the conventional surface-emitting type LED 100 is designed to emit light from a peripheral light-emitting region 120 as well as a desired emitting region 110. Therefore, in the iris scan system employing such a conventional surface-emitting type LED, the accuracy of the measurement of the object distance is deteriorated due to the light emission at the peripheral light-emitting region 120.